Hello Ben from San Diego and welcome to the forum.
Stoves, sinks, and their installation have been the subjects of many many threads here on the forum so there is no shortage of information/opinions on the subject. As has been stated, for each person you ask you will probably get a slightly different answer.
First of all, to get more galley ideas than you will ever know what to do with, you should get yourself a snack and a drink and spend a spell going through all the beautiful pictures in the galley gallery, located here http://s134.photobucket.com/user/ams-texas/slideshow/Galley%20Gallery/?albumview=slideshow
That will certainly get your creative juices flowing.
As for my own two cents....(and it's just that, and not a judgment of any kind that my way is any better or more right than anyone else's) I started out by buying a counter mounted stove and a sink, manual hand pump and all the related plumbing before I even had the walls up. By the time I actually got around to building the galley I had done a lot more research, taken a lot more measurements and just had more time to think about what I needed and wanted (and even more importantly an assessment of how I like to work). I chucked all that and went with a Coleman stove (which can sit on an extension table off my galley or on the picnic table depending on how much room I need), a portable waterjug (or a hose if campground water is available at my site) and 2 plastic dishpans. I am very happy with my decision. I use every inch of the precious storage space I have in my galley for gear and supplies. The space a sink, tanks (fresh water and gray) and a counter top stove would have occupied would have left very little space for much else. Those with bigger teardrops than mine will be less restricted in this regard so the size of trailer you intend to build will play into this.
I have lived on boats (in San Diego, coincidentally) with tiny little bar-size sinks and their function is so limited that you will get much more done (without making a wet mess in your galley) with a couple of dishpans (hence a double sink) on the picnic table. Some people have made extension tables for their trailers that have cut outs to drop in two dishpans. Bob Henry comes to mind. My thought about the stove mounted in the counter top is that it brings a lot of grease and smells into the galley, hence more cleaning. I don't particularly favor cleaning and strive to reduce the need for it whenever possible. I also tend to utilize all the space on my counter (which I would have virtually NONE OF left if I had a sink and drop in stove). Again, size matters. If you will be camping in bear country you will probably appreciate not having lingering smells of cooking meat on the inside of your galley.
Whatever you decide, it is your galley and you are the one that has to be happy with it, so evaluate your style and make it fit you. Best of luck with your build. And we are incurable voyeurs here, so please post lots of pictures!!